Effects Of Bacillus Amyloliquefaciens MG-3 On Postharvest Physiology And Storage Behavior Of 'Wuye' Litchi Fruit

Litchi(Litchi chinensis Sonn.)is a famous subtropical and tropical fruit with high nutritional value,commercial value,and health function.Since litchi fruit matured at high temperature and humidity season,the fruit quality deteriorated rapidly after harvest due to pericarp browning and fruit deterioration.And it seriously affected the litchi nutritional and commercial value.Bacillus amyloliquefaciens MG-3 is a type of biocontrol bacteria,which has a strong ability to produce secondary metabolite and inhibit the pathogenic bacteria growth and propagation.In this paper,we used 'Wuye' litchi(Litchi chinensis Sonn.cv.Wuye),the major litchi fruit cultivar in Fujian Province,China,as the experiment material,and used the fermented solution of Bacillus amyloliquefaciens MG-3,with 56 h of incubation and contain 1 ×108 CFU/mL live bacteria to treat harvested litchi fruit.This study focused on the effects of Bacillus amyloliquefaciens MG-3 on litchi physiology,quality,storage and their relationship between different,reactive oxygen,phenolics,in order to providing technical references and scientific basis for the mechanism of Bacillus amyloliquefaciens MG-3 controlling the deterioration development of harvested litchi fruit.The main results were as follows:1.Bacillus amyloliquefaciens MG-3 improved physiology,quality and storage of postharvest litchi fruit.It could delay respiration rate of litchi fruit,decreased lose weight percent,kept higher contents of titratable acid(TA),total soluble solids(TSS),sugar and vitamin C.It also delayed pericarp browning and diseasing,improved commercially acceptable fruit percentage of postharvest litchi fruit.Moreover,it maintained higher contents of chlorophyll,carotenoid,anthocyanin,flavonoid and total phenolics in pericarp of litchi fruit.2.The mechanism of Bacillus amyloliquefaciens MG-3 controlling pericarp browning of litchi fruit and relationship between reactive oxygen metabolism was investigated.It could effectively decreased the O2-· production rate of postharvest litchi fruit,reduced the contents of malondialdehyde(MDA),promoted the integrity of the cell membrane structure and reduced pericarp browning.It could keep higher activities of reactive oxygen scavenging enzymes,such as superoxide dismutase(SOD),catalase(CAT)and ascorbate peroxidase(APX).It could also keep higher the contents of reactive oxygen scavenging substance like ascorbic acid(AsA)and reduced glutathione(GSH).It maintained the 1,1-diphenyl-2-picrylhydrazyl(DPPH)scavenging ability and reduction ability.It also maintained the balance between ROS production and scavenging,alleviated the membrane peroxide.It kept higher membrane structure integrity and delayed pericarp browning of postharvest litchi fruit.3.The mechanism of Bacillus amyloliquefaciens MG-3 controlling pericarp browning of litchi fruit and phenolics metabolism was investigated.It could keep the original color of fruit pericarp and delay the pericarp browning of postharvest litchi fruit.Besides,it could keep high contents of anthocyanin,flavonoid and total phenolics in pericarp of postharvest litchi fruit.It also inhibited the activities of polyphenol oxidase of pericarp of postharvest litchi fruit,kept higher content of phenolics and delayed pericarp browning.